J. Bazoma et al.: Radioprotection 2026, 61( 2), 105 – 112 109
Fig. 2. Distribution of SSDE per examination type for overall, female and male patients, respectively.
p-value = 0.11), 5.5 ± 2.7 mGy( range: 3.7 – 15.9 mGy; p-value = 0.017) for chest, AP and CAP scans. The p-value given characterizes the statistical comparison between the SSDE values for female and male patients. It can be seen that the p-value for CAP scan is < a = 0.05. Thus, for CAP scan, the separate distributions for female and male patients should be considered. Hence, the mean SSDE value ± 1 standard deviation for female and male patients were, respectively, 6.1 ± 3.2 mGy( range: 3.7 – 15.9 mGy) and 4.3 ± 0.4 mGy( range: 3.8 – 4.9 mGy).
Table 6 presents median and 75 th percentile values of the distribution of SSDE per examination type for female, male and overall patients. It is observed that values for female patients were systematically higher than values for male patients. However, as shown above, for chest and AP scan, values for female and male patients are not statistically different.
3.4
Organ and effective doses
The details for the estimated doses to organs and tissues for head, chest, AP and CAP scans are not shown here. Table 7 shows mean and median effective doses for head, chest, AP and CAP scans.
For head scan, relevant organs and tissues that received the highest doses were the brain( median dose = 40.9 mGy; p-value = 0), the lens( median dose = 48.5 mGy; p-value = 0.005) and the salivary gland( median dose = 38.4 mGy; p-value = 0). The mean effective dose associated with head scan was 1.4 ± 0.2 mSv( median dose = 1.3 mSv; p-value = 0).
For chest scan, pertinent organs and tissues that received the highest doses were the thymus( median dose = 3.9 mGy; p-value = 0.15), the lungs( median dose = 3.5 mGy; p-value = 0.04), the breast( median dose = 3.3 mGy; p-value = 0.04) and the heart( median dose = 3.7 mGy; p-value = 0.04). The mean effective dose associated with chest scan was 2.3 ± 1.7 mSv( median dose = 1.7 mSv; p-value = 0.09).
For AP scan, organs and tissues that received the highest doses were the stomach, liver, gall bladder, spleen, pancreas, kidney, small intestine and colon. The corresponding median dose range was 4.0 – 4.9 mGy( p-value: 0.05, 0.06, 0.11 and
0.18 for kidney, gall bladder, colon and small intestine, respectively. The other organs were associated with a p-value < 0.05). The mean effective dose associated with AP scan was 2.8 ± 1.5 mSv( median dose = 2.2 mSv; p-value = 0.03).
For CAP scan, organs and tissues that received the highest doses were the stomach, the liver, gall bladder, spleen, pancreas, kidney, small intestine and colon. For these organs and tissues, the median dose range was 4.2 – 4.7 mGy( p-values < 0.05). The mean effective dose associated with CAP scan was 2.9 ± 1.7 mSv( median dose = 2.4 mSv; p-value = 0.007).
It is observed that effective doses to female patients are significantly different from effective doses to male patients( p-values < 0.05). This may be due to doses to several major organs( those associated with the highest doses, e. g., head scan: brain, lens and salivary gland; chest scan: lungs, breast and heart; AP scan: stomach, liver and spleen; CAP scan: stomach, liver and gall bladder) for female patients that are statistically different from those of male patients.
3.5 Variation in the data collected
The data collected( mAs, CTDI vol, DLP) and the dose values derived( SSDE, organ dose, effective dose) showed a large variation, particularly for chest, AP and CAP. This may be due to patient size, scan length or other factors such as the equipment used, the experience of staff, the protocols used, the complexity of the procedure( IAEA, 2013). The patient size in this study was determined in terms of effective diameter. The overall patient effective diameter ranged from 19.4 cm to 86.7 cm( CV = 49 %, chest scan), 18.8 cm to 33.0 cm( CV = 11 %, AP scan), 20.1 cm to 29.7 cm( CV = 11 %, CAP scan). The effective diameter range for female patients was 19.4 – 86.7 cm( CV = 60 %, chest scan), 18.8 – 33.0 cm( CV = 12 %, AP scan), 20.1 cm to 29.7 cm( CV = 11 %, CAP scan). The effective diameter range for male patients was 20.1 – 28.6 cm( CV = 12 %, chest scan), 21.9 – 30.4 cm( CV = 9 %, AP scan), 21.9 cm to 27.8 cm( CV = 7 %, CAP scan). This shows that women patient size contributed significantly in the large variation observed in the data collected and dose values derived, particularly for the case of chest scan. For the DLP values collected, the large variation observed is partly due to scan length, particularly that of female patients. The other causes of the observed variation may be the other factors mentioned above.
3.6 Typical DRL values: comparison with selected studies
As shown in Table 3, the study involved 308 patients distributed as follows: 199, 33, 43, and 33 patients for head, chest, AP, and CAP scans, respectively. These numbers of patients per examination are representative as the International Atomic Energy Agency( IAEA, 2018) recommends a number of patients per procedure of 10 – 20 for CT. Table 8 compares the typical DRL values determined in this study with DRL values reported in other studies. In the case of DLP, the typical value( 1172.2 mGy cm) determined for head scan is greater than DRL values proposed in Congo( 637.3 mGy cm)( Dallou, 2024), Nigeria( 1044 mGy cm)( Kabeer, 2024) and Lebanon( 1104 mGy cm)( Hakme, 2023), but lower than the value determined in Morocco( 1405.8 mGy cm)( El Fahssi, 2024).